Parking Brake System
The description of the parking brake system assumes that the service brake pedal is fully released.
Parking Brake Switch in the OFF Position
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| Illustration 1 | g01021119 |
(1) Electronic control module (ECM) (2) Parking brake switch (3) Connector (4) Monitor (5) Low brake pressure switch (6) Spool (7) Connector (8) Passage (9) Spring (10) Passage (11) Orifice (12) Brake solenoid valve (13) Piston (14) Line (15) Brake (16) Line (17) Passage (18) Override solenoid valve (19) Passage (20) Passage (21) Line (22) Connector (23) Line (24) Brake (25) Piston (26) Spring (AA) Park brake (N/C) (BB) Park brake (N/O) (CC) Parking brake pressure switch (DD) Proportional driver return (EE) Override solenoid (FF) Parking brake solenoid (GG) 10 Volt sensor return (HH) Line to "PS1" port on the rear piston pump (JJ) Line to "PS1" port on the front piston pump (KK) Line from the rear charge pump (MM) Supply power from the fuse panel (L1) LED for the engine oil pressure indicator (L2) LED for the hydraulic oil filter bypass indicator (L3) LED for the indicator for the hydrostatic system (L4) LED for the parking brake indicator (L5) LED for the alternator indicator light (L6) LED for the air inlet heater indicator light | |
When parking brake switch (2) is in the OFF position, parking brake switch (2) completes the circuit between wire J764-BR-18 and wire A314-OR-18. The completed circuit results in a signal of 0 volts to ECM (1) at pin 33 of the J1 connector.
ECM (1) sends a signal of 12 volts from pin 68 of the J1 connector. The signal flows through wire A958-WH-18 through connector (22) to solenoid valve (12). The signal flows through the coil of solenoid valve (12) through connector (22) through wire H803-BU-18 to ECM (1) through pin 55 of the J1 connector.
As the signal flows through the coil of solenoid valve (12), solenoid valve (12) is shifted upward. Pilot oil from charge pump (KK) flows through passage (19) to solenoid valve (12). The oil flows from solenoid valve (12) through passage (20) to line (23). The oil flows through line (23) and splits to line (16) and to line (21) .
The oil flows through line (21) to piston (25). The oil overcomes the force of spring (26) and the oil forces piston (25) to move downward from brake pack (24). Then, the right piston motor is free to rotate.
The oil also flows through line (16) to piston (13). The oil overcomes the force of spring (9) and the oil forces piston (13) to move upward from brake pack (15). Then, the left piston motor is free to rotate.
As the pressure in line (16) increases, the pressure oil opens low brake pressure switch (5) and the switch opens the circuit between wire J764-BR-18 and wire C491-PU-18. The open circuit results in a floating state in wire C491-PU-18. Since wire C491-PU-18 to low brake pressure switch (5) is in a floating state, wire C491-PU-18 to monitor (4) is also in a floating state and LED (L4) turns off.
ECM (1) also sends a signal of 12 volts from pin 67 of the J1 connector. The signal flows through wire 915-GR-18 through connector (7) to solenoid valve (18). The signal flows through the coil of solenoid valve (18) through connector (7) to wire H803-BU-18. The signal flows through wire H803-BU-18 to ECM (1) through pin 55 of the J1 connector.
As the signal flows through the coil of solenoid valve (18), solenoid valve (18) shifts downward. Pilot oil from charge pump (KK) flows through passage (19) to solenoid valve (18). The oil flows from solenoid valve (18) through passage (17) to spool (6). The pressure of the pilot oil in passage (17) overcomes the force of the spring against spool (6) and spool (6) shifts to the right. Spool (6) blocks pilot oil from line (HH) to line (14) and pilot oil from line (JJ) to line (14) .
As spool (6) shifts to the right, oil in passage (8) flows through solenoid valve (18) through passage (10) to line (14). Then, the oil flows through line (14) back to the hydraulic tank.
Parking Brake Switch in the ON position
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| Illustration 2 | g01021422 |
(1) Electronic control module (ECM) (2) Parking brake switch (3) Connector (4) Monitor (5) Low brake pressure switch (6) Spool (7) Connector (8) Passage (9) Spring (10) Passage (11) Orifice (12) Brake solenoid valve (13) Piston (14) Line (15) Brake (16) Line (17) Passage (18) Override solenoid valve (19) Passage (20) Passage (21) Line (22) Connector (23) Line (24) Brake (25) Piston (26) Spring (AA) Park brake (N/C) (BB) Park brake (N/O) (CC) Parking brake pressure switch (DD) Proportional driver return (EE) Override solenoid (FF) Parking brake solenoid (GG) 10 Volt sensor return (HH) Line to "PS1" port on the rear piston pump (JJ) Line to "PS1" port on the front piston pump (KK) Line from the rear charge pump (MM) Supply power from the fuse panel (L1) LED for the engine oil pressure indicator (L2) LED for the hydraulic oil filter bypass indicator (L3) LED for the indicator for the hydrostatic system (L4) LED for the parking brake indicator (L5) LED for the alternator indicator light (L6) LED for the air inlet heater indicator light | |
When parking brake switch (2) is in the ON position, parking brake switch (2) completes the circuit between wire J764-BR-18 and wire A315-WH-18. The completed circuit results in a signal of 0 volts to ECM (1) at pin 34 of the J1 connector.
ECM (1) sends a signal of 0 volts from pin 68 of the J1 connector. The signal flows through wire A958-WH-18 through connector (22) to solenoid valve (12). The signal flows through the coil of solenoid valve (12) through connector (22) through wire H803-BU-18 to ECM (1) through pin 55 of the J1 connector.
Since the signal through the coil of solenoid valve (12) is 0 volts, solenoid valve (12) shifts downward. Pilot oil from charge pump (KK) through passage (19) is blocked at solenoid valve (12). Oil from piston (13) flows through line (16) to line (23) and oil from piston (25) flows through line (21) to line (23). The oil flows through line (23) to passage (20). The oil flows from passage (20) through solenoid valve (12) to orifice (11). The oil flows from orifice (11) through passage (10) to line (14). The oil flows through line (14) back to the hydraulic tank. As the oil flows from piston (13), spring (9) forces piston (13) against brake (15). As the oil flows from piston (25), spring (26) forces piston (25) against brake (24). Then, the brakes are engaged.
As the oil pressure in line (16) decreases, low brake pressure switch (5) closes. As pressure switch (5) closes, pressure switch (5) completes the circuit between wire J764-BR-18 and wire C491-PU-18. A signal of 0 volts flows from wire J764-BR-18 through connector (3) to pressure switch (5). The signal flows through pressure switch (5) through connector (3) to wire C491-PU-18. The signal flows through wire C491-PU-18 to ECM (1) through pin 43 of the J1 connector.
Since the signal for wire C491-PU-18 to ECM (1) is 0 volts, the signal for wire C491-PU-18 to monitor (4) is 0 volts. The signal flows through wire C491-PU-18 to monitor (4) and LED (L4) turns on.
Service Brake System
The description of the service brake system assumes that the parking brake switch is in the OFF position and the direction/speed control lever is in the FORWARD position. For additional information regarding the power train system, refer to Systems Operation, "Power Train Hydraulic System".
The Service Brake Pedal Released.
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| Illustration 3 | g01021589 |
(1) Electronic control module (ECM) (2) Parking brake switch (3) Spring (4) Brake (5) Spool (6) Line (7) Piston (8) Line (9) Passage (10) Passage (11) Actuator piston (12) Passage (13) Servo valve (14) Left piston motor (15) Low brake pressure switch (16) Line (17) Brake solenoid valve (18) Monitor (19) Line (20) Orifice (21) Line (22) Connector (23) Passage (24) Passage (25) Passage (26) Override solenoid valve (27) Connector (28) Connector (29) Line (30) Front piston pump (31) Connector (32) Rear piston pump (33) Line (34) Passage (35) Passage (36) Connector (37) Actuator piston (38) Actuator piston (39) Orifice (40) Passage (41) Orifice (42) Orifice (43) Passage (44) Orifice (45) Passage (46) Servo valve (47) Passage (48) Passage (49) Connector (50) Service brake position sensor (51) Connector (52) Servo valve (53) Passage (54) Connector (55) Connector (56) Passage (57) Passage (58) Connector (59) Piston (60) Servo valve (61) Actuator piston (62) Spring (63) Brake (64) Right piston motor (65) Switch (AA) Service brake pedal switch (N/C) (BB) Park brake N/C (CC) Service brake pedal position sensor (DD) Park brake (N/O) (EE) Service brake pedal switch (N/O) (FF) Parking brake pressure switch (GG) 8 volt sensor supply (HH) Left pump forward steer solenoid (JJ) Left pump reverse steer solenoid (KK) Proportional driver return (MM) Right pump forward steer solenoid (NN) Right pump reverse steer solenoid (PP) Proportional driver return (RR) Left motor solenoid (SS) Right motor solenoid (TT) Proportional driver return (VV) Override solenoid (WW) Parking brake solenoid (XX) 10 volt sensor return (YY) Supply power from the fuse panel (ZZ) + Battery (A1) Ground (B1) Signal (L1) LED for the engine oil pressure indicator (L2) LED for the hydraulic oil filter bypass indicator (L3) LED for the indicator for the hydrostatic system (L4) LED for the parking brake indicator (L5) LED for the alternator indicator light (L6) LED for the air inlet heater indicator light | |
When the service brake pedal is fully released, pedal position sensor (50) sends a pulse width modulated signal with a 56.2% duty cycle. The signal flows from pedal position sensor (50) through connector (49) to wire G745-PK-18. The signal flows through wire G745-PK-18 to ECM (1) through pin 28 of the J2 connector.
Also, when the service brake pedal is fully released, switch (65) closes the circuit between wire J764-BR-18 and wire F931-PK-18. ECM (1) also interprets this signal as a full release of the service brake pedal.
Since ECM (1) registers the signals as the release of the service brake pedal, ECM (1) does not modify any signals to the servo valves of the pumps or to the servo valves of the motors. Also, ECM (1) does not modify any signals to solenoid valve (26) or to solenoid valve (17). Refer to "Parking Brake Switch in the OFF Position" for additional information regarding the operation of brake solenoid valve (17) and of override solenoid valve (26) .
The Service Brake Pedal Is Partially Depressed
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| Illustration 4 | g01023636 |
(1) Electronic control module (ECM) (2) Parking brake switch (3) Spring (4) Brake (5) Spool (6) Line (7) Piston (8) Line (9) Passage (10) Passage (11) Actuator piston (12) Passage (13) Servo valve (14) Left piston motor (15) Low brake pressure switch (16) Line (17) Brake solenoid valve (18) Monitor (19) Line (20) Orifice (21) Line (22) Connector (23) Passage (24) Passage (25) Passage (26) Override solenoid valve (27) Connector (28) Connector (29) Line (30) Front piston pump (31) Connector (32) Rear piston pump (33) Line (34) Passage (35) Passage (36) Connector (37) Actuator piston (38) Actuator piston (39) Orifice (40) Passage (41) Orifice (42) Orifice (43) Passage (44) Orifice (45) Passage (46) Servo valve (47) Passage (48) Passage (49) Connector (50) Service brake pedal position sensor (51) Connector (52) Servo valve (53) Passage (54) Connector (55) Connector (56) Passage (57) Passage (58) Connector (59) Piston (60) Servo valve (61) Actuator piston (62) Spring (63) Brake (64) Right piston motor (65) Switch (AA) Service brake pedal switch (N/C) (BB) Park brake (N/C) (CC) Service brake pedal position sensor (DD) Park brake (N/O) (EE) Service brake pedal switch (N/O) (FF) Parking brake pressure switch (GG) 8 volt sensor supply (HH) Left pump forward steer solenoid (JJ) Left pump reverse steer solenoid (KK) Proportional driver return (MM) Right pump forward steer solenoid (NN) Right pump reverse steer solenoid (PP) Proportional driver return (RR) Left motor solenoid (SS) Right motor solenoid (TT) Proportional driver return (VV) Override solenoid (WW) Parking brake solenoid (XX) 10 volt sensor return (YY) Supply power from the fuse panel (ZZ) + Battery (A1) Ground (B1) Signal (L1) LED for the engine oil pressure indicator (L2) LED for the hydraulic oil filter bypass indicator (L3) LED for the indicator for the hydrostatic system (L4) LED for the parking brake indicator (L5) LED for the alternator indicator light (L6) LED for the air inlet heater indicator light | |
As you start to depress the service brake pedal, the duty cycle of the pulse width modulated signal from pedal position sensor (50) decreases. The signal flows from pedal position sensor (50) through connector (49) to wire G745-PK-18. The signal flows through wire G745-PK-18 to ECM (1) through pin 28 of the J2 connector.
As ECM (1) interprets the decreased duty cycle, ECM (1) modifies the signals to the servo valves of the pumps and to the servo valves of the motors. ECM (1) starts to decrease the duty cycle of the pulse width modulated signals to servo valve (13) and to servo valve (60). As the duty cycles of the signals decrease, piston motor (14) and piston motor (64) start to upstroke and the machine begins to slow down.
When the piston motors reach the maximum displacements and you continue to depress the service brake pedal, ECM (1) starts to decrease the duty cycle of the pulse width modulated signals to servo valve (46) and to servo valve (52). As the duty cycles of the signals decrease, front piston pump (30) and rear piston pump (32) start to destroke and the machine continues to slow down until the pumps reach zero angle.
The Service Brake Pedal Is Fully Depressed
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| Illustration 5 | g01023638 |
(1) Electronic control module (ECM) (2) Parking brake switch (3) Spring (4) Brake (5) Spool (6) Line (7) Piston (8) Line (9) Passage (10) Passage (11) Actuator piston (12) Passage (13) Servo valve (14) Left piston motor (15) Low brake pressure switch (16) Line (17) Brake solenoid valve (18) Monitor (19) Line (20) Orifice (21) Line (22) Connector (23) Passage (24) Passage (25) Passage (26) Override solenoid valve (27) Connector (28) Connector (29) Line (30) Front piston pump (31) Connector (32) Rear piston pump (33) Line (34) Passage (35) Passage (36) Connector (37) Actuator piston (38) Actuator piston (39) Orifice (40) Passage (41) Orifice (42) Orifice (43) Passage (44) Orifice (45) Passage (46) Servo valve (47) Passage (48) Passage (49) Connector (50) Service brake pedal position sensor (51) Connector (52) Servo valve (53) Passage (54) Connector (55) Connector (56) Passage (57) Passage (58) Connector (59) Piston (60) Servo valve (61) Actuator piston (62) Spring (63) Brake (64) Right piston motor (65) Switch (AA) Service brake pedal switch (N/C) (BB) Park brake (N/C) (CC) Service brake pedal position sensor (DD) Park brake (N/O) (EE) Service brake pedal switch (N/O) (FF) Parking brake pressure switch (GG) 8 volt sensor supply (HH) Left pump forward steer solenoid (JJ) Left pump reverse steer solenoid (KK) Proportional driver return (MM) Right pump forward steer solenoid (NN) Right pump reverse steer solenoid (PP) Proportional driver return (RR) Left motor solenoid (SS) Right motor solenoid (TT) Proportional driver return (VV) Override solenoid (WW) Parking brake solenoid (XX) 10 volt sensor return (YY) Supply power from the fuse panel (ZZ) + Battery (A1) Ground (B1) Signal (L1) LED for the engine oil pressure indicator (L2) LED for the hydraulic oil filter bypass indicator (L3) LED for the indicator for the hydrostatic system (L4) LED for the parking brake indicator (L5) LED for the alternator indicator light (L6) LED for the air inlet heater indicator light | |
When the service brake pedal is fully depressed, pedal position sensor (50) sends a pulse width modulated signal through connector (49) to wire G745-PK-18. The signal flows through wire G745-PK-18 to ECM (1) through pin 28 of the J2 connector. When ECM (1) receives a signal with a duty cycle between 35% and 31%, ECM (1) interprets the signal as full depression of the service brake pedal.
ECM (1) modifies the signals to the piston motors in order to return the piston motors to the maximum displacement. Also, ECM (1) modifies the signals to the piston pumps in order to return the piston pumps to zero angle.
Also, when the service brake pedal is fully depressed, switch (65) closes the circuit between wire J764-BR-18 and wire C992-PU-18. ECM (1) also interprets this signal as full depression of the service brake pedal.
ECM (1) sends a signal of 0 volts from pin 68 of the J1 connector. The signal flows through wire A958-WH-18 through connector (27) to solenoid valve (17) .
Since the signal to solenoid valve (17) is 0 volts, solenoid valve (14) shifts downward. Pilot oil from the charge pump in passage (23) is blocked at solenoid valve (17). Oil from piston (7) flows through line (16) to line (29) and oil from piston (59) flows through line (33) to line (29). The oil flows through line (29) through solenoid valve (17) to orifice (20). The oil flows from orifice (20) through passage (12) to line (21). The oil flows through line (21) back to the hydraulic tank. As the oil flows from piston (7), spring (3) forces piston (7) against brake (4). As the oil flows from piston (59), spring (62) forces piston (59) against brake (63). Then, the brakes are engaged.
As the oil pressure in line (16) decreases, low brake pressure switch (15) closes. As pressure switch (15) closes, pressure switch (15) completes the circuit between wire J764-BR-18 and wire C491-PU-18. A signal of 0 volts flows from wire J764-BR-18 through connector (28) to pressure switch (15). The signal flows through pressure switch (15) through connector (28) to wire C491-PU-18. The signal flows through wire C491-PU-18 to ECM (1) through pin 43 of the J1 connector.
Since the signal for wire C491-PU-18 to ECM (1) is 0 volts, the signal for wire C491-PU-18 to monitor (18) is 0 volts. The signal flows through wire C491-PU-18 to monitor (18) and LED (L4) turns on.